The Legal, Economic and Social Dimensions of the Eectiveness of Public ProcurementModern economies of European countries are characterised by a considerable share of public expenditure in their gross domestic product. A large portion of such expenses is effected through a system of public procurement. The current value of that market in Poland is estimated at around PLN 150 billion. What much matters for the correct functioning of that market in Poland and the EU is an effective policy of public procurement, a vital tool of economic and social intervention. With time, such a policy should contribute to the effective allocation of resources, economic development of the Member States and job creation. An important instrument which may help deliver this vision is the new approach to public procurement, a notion that includes activities aiming at creating legal and institutional conditions that would ensure as effective use of public funds as possible and contribute to elimi- nating the barriers in access to the procurement market experienced by SMEs. The effectiveness of public procurement and instruments to deliver it should be considered in the legal, economic and social context. It is a complex and multidimensional issue. Discussion of all those aspects together paints a picture of the public sector as an intelligent client of the public procurement system, aware of its legal opportunities and limitations, using a cost and benefit analysis as well as the rule of best value for money, and having a good market sense. The intelligent contracting authority is also aware of the social effects of the performance of public contracts, e.g. as regards better quality of life or furthering trust in the financial operations by public bodies.